The AFR 180's are, in my opinion, the finest heads you can bolt onto a 355 Chevy to make power in a street-friendly rpm range. This AFR page has the flow chart at the bottom.....
Click "dyno tests" at the top of this page, then click "Chevy Dyno Tested Packages". You'll see 3 builds using 180 heads. 420hp, 430hp and 450hp. Choose one, purchase the components listed and bolt your killer together.